Two hundred fifty-seven years ago, King George II drew a boundary line separating New Hampshire and Maine and the line stood, largely uncontested, for more than 200 years. Then Maine instituted its income tax and suddenly the precise location of the line became highly questionable to the residents of New Hampshire — at least those who are employed at Portsmouth Naval Shipyard on Seavey Island in Maine.

“That the dividing line shall pass up thro the Mouth of the Piscatqua Harbor and up the middle of the River …” the cartographer-king wrote in 1740, forever placing Seavey Island in Kittery, Maine. That has not stopped New Hampshire from trying to shove the state border to the other side of the island or, failing that, forcing Maine to stop taxing New Hampshire residents who work in Maine. A substantial body of precedents suggests that the Granite State will not win this round of the debate either.

The question gained new urgency late last month when the New Hampshire governor, Jeanne Shaheen, said she discovered a British map from 1761 that placed Seavey Island in New Hampshire. But the earlier description of the king’s intention shows that what she may have discovered, if her assessment of the map proves accurate, is a 236-year-old typo, which might be valuable as a curiosity but not very useful in this debate, considering that the line was set 21 years before the governor’s map was made.

If King George II isn’t persuasive enough, how about the U.S. Supreme Court? In a 1976 case similar to the issues being debated now, the court held that, “The terms `Middle of the River’ and `Middle of the Harbor,’ as used in the [1740] Order, mean the middle of the main channel of navigation of the Piscataqua River and the middle of main channel of navigation of Gosport Harbor.”

That puts Seavey Island in Maine. And as Maine Attorney General Andrew Ketterer recently testified before the Senate, New Hampshire seems to have concluded this some years earlier all by itself. Back in 1969, the New Hampshire Attorney General George S. Papagianis concluded that the shipyard “is territorially a part of the State of Maine.” New Hampshire’s own state maps show Seavey Island in Maine and New Hampshire did not protest when the federal government turned to Maine as the state to establish concurrent jurisdiction for the island shipyard.

The boundary question is really a tax question, but it turned out not to be the tax question that the Senate’s State Governmental Affairs Committee rejected last week that would have attached the naval station debate to a bill concerning three federal facilities that straddle the border of two states. As Sen. Susan Collins recently pointed out, because workers at these other facilities do not enter their neighboring state except when at work and on federal property, they do not benefit from the services of that state. That clearly is not the case for New Hampshire workers traveling into Maine.

All that is left for New Hampshire is to argue that its almost 1,400 residents working at the shipyard should not have to pay income taxes in Maine simply because they don’t want to. This argument may find some sympathy among Maine resident taxpayers, but is not likely to carry the day in a court.